Jest: How to mock one specific method of a class

Question

Let\'s suppose I have the following class:

export default class Person {
    constructor(first, last) {
        this.first = first;
        this.last = last         


        

Answer 1

If you are using Typescript, you can do the following:

Person.prototype.sayMyName = jest.fn().mockImplementationOnce(async () => 
        await 'my name is dev'
);

And in your test, you can do something like this:

const person = new Person();
const res = await person.sayMyName();
expect(res).toEqual('my name is dev');

Hope this helps someone!